Oxide catalyst for oxidation or ammoxidation

ABSTRACT

Disclosed is an oxide catalyst for use in catalytic oxidation or ammoxidation of propane or isobutane in the gaseous phase, which comprises a composition represented by the Mo 1 V a Sb b Nb c Z d O n  (wherein: Z is at least one element selected from the group consisting of tungsten, chromium, titanium, aluminum, tantalum, zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth, yttrium, gallium, rare earth elements and alkaline earth metals: and a, b, c, d, and n are, respectively, the atomic ratios of V, Sb, Nb, Z and O, relative to Mo), wherein 0.1≦a&lt;0.4, 0.1&lt;b≦0.4, 0.01≦c≦0.3, 0≦d≦1, with the proviso that a&lt;b, and n is a number determined by and consistent with the valence requirements of the other elements present. Also disclosed is a process for producing an unsaturated carboxylic acid or an unsaturated nitrile by using the above-mentioned oxide catalyst.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an oxide catalyst for use incatalytic oxidation or ammoxidation of propane or isobutane in thegaseous phase. More particularly, the present invention is concernedwith an oxide catalyst for use in catalytic oxidation or ammoxidation ofpropane or isobutane in the gaseous phase, which comprises, in aspecific ratio, molybdenum (Mo), vanadium (V), antimony (Sb), niobium(Nb), oxygen (O) and at least one element Z selected from the groupconsisting of tungsten, chromium, titanium, aluminum, tantalum,zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel,palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth,yttrium, gallium, rare earth elements and alkaline earth metals, whereinthe Sb/Mo atomic ratio (b) is larger than V/Mo atomic ratio (a), and theSb/Mo atomic ratio (b) does not exceed 0.4. By the use of the oxidecatalyst of the present invention in the oxidation or ammoxidation ofpropane or isobutane in the gaseous phase, (meth)acrylonitrile or(meth)acrylic acid can be produced with high selectivity and such highselectivity can be maintained for a long time, so that(meth)acrylonitrile or (meth)acrylic acid can be efficiently producedfor a long time.

[0003] The present invention is also concerned with a process forproducing an unsaturated carboxylic acid or an unsaturated nitrile inthe presence of the abovementioned oxide catalyst.

[0004] 2. Prior Art

[0005] Conventionally, there have been well known a process forproducing (meth)acrylonitrile by ammoxidation of propylene orisobutylene, and a process for producing (meth)acrylic acid by oxidationof propylene or isobutylene. Recently, as substitutes for such processesfor the ammoxidation or oxidation of propylene or isobutylene, attentionhas been attracted to a process for producing (meth)acrylonitrile or(meth)acrylic acid by a catalytic ammoxidation or oxidation in thegaseous phase, wherein propane or isobutane is used as a raw materialinstead of propylene or isobutylene. As catalysts for use in theseprocesses, a number of catalysts have been proposed.

[0006] Of the catalysts proposed, especially, an oxide catalystcomprising Mo—V—Sb—Nb has been attracting attention, since such an oxidecatalyst has advantages in that the catalyst comprises elements having arelatively low volatility, the catalyst can be used for a catalyticammoxidation or oxidation in the gaseous phase at a low reactiontemperature, and (meth)acrylonitrile or (meth)acrylic acid can beproduced with relatively high selectivity and in relatively high yield.

[0007] Methods for producing (meth)acrylonitrile in the presence of theoxide catalyst comprising Mo—V—Sb—Nb (hereinafter, frequently referredto as an “Mo—V—Sb—Nb oxide catalyst”) are disclosed in various patentdocuments, such as Unexamined Japanese Patent Application Laid-OpenSpecification Nos. 9-157241 (corresponding to U.S. Pat. No. 5,750,760and EP 0767164 A1), 10-28862, 10-81660, 10-310539, 10-330343, 11-42434,11-43314, 11-57479, 11-263745, 2000-1464, 2000-143244, WO 0012209 A1(corresponding to DE 1998325 T), and U.S. Pat. No. 6,043,185.

[0008] Methods for producing (meth)acrylic acid in the presence of theMo—V—Sb—Nb oxide catalyst are also disclosed in various patentdocuments, such as Unexamined Japanese Patent Application Laid-OpenSpecification Nos. 9-316023, 10-118491, 10-120617 (corresponding to U.S.Pat. Nos. 5,994,580 and 6,060,422), 10-137585, 11-285637, 11-343261,2000-51693, 11-343262, 10-36311, 10-45664, 9-278680 and 10-128112.

[0009] Each of the above-mentioned Mo—V—Sb—Nb oxide catalysts, which areused for producing (meth)acrylonitrile or (meth)acrylic acid, comprisesan oxide represented by the following formula (a):

Mo₁V_(p)Sb_(q)Nb_(r)O_(m)  (a)

[0010] wherein p, q, r and m are, respectively, the atomic ratios of V,Sb, Nb and O, relative to Mo.

[0011] The above-mentioned conventional Mo—V—Sb—Nb oxide catalysts canbe categorized into the following two groups:

[0012] (i) catalysts in which the V/Mo atomic ratio is equal to orlarger than the Sb/Mo atomic ratio, i.e., p and q in formula (a) abovesatisfy the following relationship: p≧q; and

[0013] (ii) catalysts in which the Sb/Mo atomic ratio is larger thanV/Mo atomic ratio, i.e., p and q in formula (a) above satisfy thefollowing relationship: p<q,

[0014] wherein the Sb/Mo atomic ratio is equal to or larger than 0.5,i.e., q in formula (a) above satisfies the following relationship:q≧0.5.

[0015] When the conventional Mo—V—Sb—Nb oxide catalysts mentioned aboveare used, (meth)acrylonitrile or (meth)acrylic acid is sometimesproduced with a relatively high selectivity (hereinafter,(meth)acrylonitrile or (meth)acrylic acid is frequently referred to asthe “desired product”). However, the selectivity for the desiredproduct, which is achieved by such conventional catalysts, is notsatisfactory.

[0016] Of the Mo—V—Sb—Nb oxide catalysts of group (i) above, oxidecatalysts capable of achieving a relatively high selectivity for thedesired product exhibits a disadvantageously low stability.Specifically, especially when the catalytic oxidation or ammoxidation inthe gaseous phase is performed in the presence of each of such oxidecatalysts in a recycling mode using a gaseous feedstock mixture having ahigh partial pressure of propane, the selectivity for the desiredproduct decreases with the lapse of time.

[0017] In an attempt to improve the stability of the Mo—V—Sb—Nb oxidecatalysts of group (i) above so as to maintain the selectivity for thedesired product at a high level, the following two methods have beenproposed:

[0018] a first method in which, using a reactor having a zone in which agaseous mixture having a higher oxygen concentration than that of agaseous reaction mixture produced is contacted with the oxide catalyst,the oxide catalyst is continuously oxidized to regenerate the oxidecatalyst (see Unexamined Japanese Patent Application Laid-OpenSpecification No. 11-263745); and

[0019] a second method in which an Mo—V—Sb—Nb oxide catalyst of group(i) above produced by a process comprising preparing a raw materialliquid mixture for the catalyst, followed by spray-drying andcalcination is mixed with an aqueous solution containing Mo and Co toobtain an aqueous mixture, and the obtained aqueous mixture isspray-dried and calcined to thereby obtain a modified catalystcontaining a large amount of an Mo—Co composite oxide (see UnexaminedJapanese Patent Application Laid-Open Specification No. 11-57479).

[0020] Of the above-mentioned two methods, the first method isdisadvantageous in that the process for the catalytic ammoxidation oroxidation in the gaseous phase inevitably becomes cumbersome. On theother hand, the second method is also disadvantageous not only in thatthe process for producing the oxide catalyst becomes too cumbersome, butalso in that, even when silica is used to increase the strength of thecatalyst, since the oxide catalyst produced in the second methodcontains a large amount of an Mo—Co composite oxide, it is difficult tocause the oxide catalyst to contain a satisfactory amount of silicawhich is needed to satisfactorily increase the strength of the oxidecatalyst. Therefore, especially, it is difficult to apply the secondmethod to the production of an oxide catalyst which is used for areaction in a fluidized bed and, hence, is required to have a highstrength.

[0021] With respect to the Mo—V—Sb—Nb oxide catalysts of group (ii)above, these catalysts have a disadvantage in that the selectivity forthe desired product is low.

[0022] From the above, it is apparent that, by the conventionalMo—V—Sb—Nb oxide catalysts for the catalytic ammoxidation or oxidation,it is difficult to stably produce the desired compound with highselectivity for a long time.

SUMMARY OF THE INVENTION

[0023] In this situation, the present inventors have made extensive andintensive studies toward developing an Mo—V—Sb—Nb oxide catalyst whichcan be used for stably producing (meth)acrylonitrile or (meth)acrylicacid with high selectivity for a long time. As a result, it hasunexpectedly been found that, by the use of a Mo—V—Sb—Nb oxide catalysthaving a specific composition in the oxidation or ammoxidation ofpropane or isobutane in the gaseous phase, (meth)acrylonitrile or(meth)acrylic acid can be produced with high selectivity and such highselectivity can be maintained for a long time. The above-mentionedMo—V—Sb—Nb oxide catalyst having a specific composition comprises, in aspecific ratio, molybdenum (Mo), vanadium (V), antimony (Sb), niobium(Nb), oxygen (O) and at least one element Z selected from the groupconsisting of tungsten, chromium, titanium, aluminum, tantalum,zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel,palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth,yttrium, gallium, rare earth elements and alkaline earth metals, whereinthe Sb/Mo atomic ratio (b) is larger than V/Mo atomic ratio (a), and theSb/Mo atomic ratio (b) does not exceed 0.4. Based on these novelfindings, the present invention has been completed.

[0024] Accordingly, it is a primary object of the present invention toprovide an Mo—V—Sb—Nb oxide catalyst which can be advantageously usedfor stably producing (meth)acrylonitrile or (meth)acrylic acid with highselectivity for a long time.

[0025] Another object of the present invention is to provide a processfor producing (meth)acrylonitrile, which comprises performingammoxidation in the presence of the above-mentioned oxide catalyst, anda process for producing (meth)acrylic acid, which comprises performingoxidation in the presence of the abovementioned oxide catalyst.

[0026] The foregoing and other objects, features and advantages of thepresent invention will be apparent from the following detaileddescription and appended claims taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

[0027] In the drawings:

[0028]FIG. 1 is an X-ray diffraction pattern of the oxide catalystobtained in Example 1; and

[0029]FIG. 2 is an enlarged view of the X-ray diffraction pattern ofFIG. 1, showing the range of from 25 to 30° in terms of the diffractionangle (2θ), in order to explain how to obtain the peak intensity ratio.

DESCRIPTION OF REFERENCE NUMERALS

[0030] A₁: Apex of the peak observed at diffraction angle (2θ) of27.1±0.3° in an X-ray diffraction pattern of the oxide catalyst obtainedusing CuK_(α) as a source of X-ray;

[0031] A₂: Apex of the peak observed at diffraction angle (2θ) of28.1±0.3° in an X-ray diffraction pattern of the oxide catalyst obtainedusing CuK_(α) as a source of X-ray;

[0032] B₁: Point at which the curved line of the X-ray diffractionpattern exhibits a minimum intensity value in the diffraction angle (2θ)range of 26.4±0.3°;

[0033] B₂: Point at which the curved line of the X-ray diffractionpattern exhibits a minimum intensity value in the diffraction angle (2θ)range of 27.6±0.3°;

[0034] B₃: Point at which the curved line of the X-ray diffractionpattern exhibits a minimum intensity value in the diffraction angle (2θ)range of 28.8±0.3°;

[0035] C₁: Point at which a straight line drawn downwardly from peakapex A₁ vertically to the 2θ-axis intersects with a straight lineconnecting points B₁ and B₂; and

[0036] C₂: Point at which a straight line drawn downwardly from peakapex A₂ vertically to the 2θ-axis intersects with a straight lineconnecting points B₂ and B₃.

DETAILED DESCRIPTION OF THE INVENTION

[0037] According to the present invention, there is provided an oxidecatalyst for use in catalytic oxidation or ammoxidation of propane orisobutane in the gaseous phase, which comprises a compositionrepresented by the following formula (I):

Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I)

[0038] wherein:

[0039] Z is at least one element selected from the group consisting oftungsten, chromium, titanium, aluminum, tantalum, zirconium, hafnium,manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium,platinum, zinc, boron, indium, germanium, tin, lead, bismuth, yttrium,gallium, rare earth elements and alkaline earth metals; and

[0040] a, b, c, d, and n are, respectively, the atomic ratios ofvanadium (V), antimony (Sb), niobium (Nb), Z and oxygen (O), relative tomolybdenum (Mo),

[0041] wherein:

[0042] 0.1≦a<0.4,

[0043] 0.1<b≦0.4,

[0044] 0.01≦c≦0.3,

[0045] 0≦d≦1,

[0046] with the proviso that a<b, and n is a number determined by andconsistent with the valence requirements of the other elements present.

[0047] For easy understanding of the present invention, the essentialfeatures and various preferred embodiments of the present invention areenumerated below.

[0048] 1. An oxide catalyst for use in catalytic oxidation orammoxidation of propane or isobutane in the gaseous phase, whichcomprises a composition represented by the following formula (I):

Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I)

[0049] wherein:

[0050] Z is at least one element selected from the group consisting oftungsten, chromium, titanium, aluminum, tantalum, zirconium, hafnium,manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium,platinum, zinc, boron, indium, germanium, tin, lead, bismuth, yttrium,gallium, rare earth elements and alkaline earth metals; and

[0051] a, b, c, d, and n are, respectively, the atomic ratios ofvanadium (V), antimony (Sb), niobium (Nb), Z and oxygen (O), relative tomolybdenum (Mo),

[0052] wherein:

[0053] 0.1≦a<0.4,

[0054] 0.1<b ≦0.4,

[0055] 0.01≦c≦0.3,

[0056] 0≦d≦1,

[0057] with the proviso that a<b, and n is a number determined by andconsistent with the valence requirements of the other elements present.

[0058] 2. The oxide catalyst according to item 1 above, wherein a informula (I) satisfies the following relationship: 0.1≦a≦0.3.

[0059] 3. The oxide catalyst according to item 1 above, wherein b informula (I) satisfies the following relationship: 0.1<b≦0.35.

[0060] 4. The oxide catalyst according to item 1 above, wherein c informula (I) satisfies the following relationship: 0.05≦c≦0.2.

[0061] 5. The oxide catalyst according to item 1 above, wherein a informula (I) satisfies the following relationship: 0.15≦a≦0.28.

[0062] 6. The oxide catalyst according to item 1 above, wherein b informula (I) satisfies the following relationship: 0.2≦b≦0.33.

[0063] 7. The oxide catalyst according to item 1 above, wherein c informula (I) satisfies the following relationship: 0.05≦c≦0.15.

[0064] 8. The oxide catalyst according to item 1 above, wherein a, b andc in formula (I) satisfy the following relationships:

[0065] 0.15≦a≦0.28;

[0066] 0.2≦b≦0.33;

[0067] 0.05≦c≦0.15;

[0068] 0.5≦a+b+c≦0.69; ${\frac{a}{a + b + c} \geq 0.23};\quad {and}$${0.59 - \frac{0.528a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.7 - {\frac{0.524a}{a + b + c}.}}$

[0069] 9. The oxide catalyst according to item 1 above, wherein a, b andc in formula (I) satisfy the following relationships:

[0070] 0.16≦a≦0.28;

[0071] 0.24≦b≦0.33;

[0072] 0.07≦c≦0.15;

[0073] 0.53≦a+b+c≦0.67; ${\frac{a}{a + b + c} \geq 0.26};\quad {and}$${0.63 - \frac{0.549a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.68 - {\frac{0.529a}{a + b + c}.}}$

[0074] 10. The oxide catalyst according to item 1 above, wherein a, band c in formula (I) satisfy the following relationships:

[0075] 0.16 ≦a≦0.26;

[0076] 0.24≦b≦0.30;

[0077] 0.08≦c≦0.12;

[0078] 0.57≦a+b+c≦0.60; ${\frac{a}{a + b + c} \geq 0.28};\quad {and}$${0.67 - \frac{0.5975a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.67 - {\frac{0.5352a}{a + b + c}.}}$

[0079] 11. The oxide catalyst according to item 1 above, which exhibits,in an X-ray diffraction pattern thereof obtained using CuK_(α) as asource of X-ray, peaks at diffraction angles (2θ) of:

[0080] 22.1±0.3°, 28.1±0.3°, 36.1±0.3° and 45.2±0.3°;

[0081] 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 35.2±0.3°and 45.2±0.3°;or

[0082] 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 28.1±0.3°, 35.2±0.3°,36.1±0.3° and 45.2±0.3°.

[0083] 12. The oxide catalyst according to item 1 above, which furthercomprises a silica carrier having supported thereon the oxide catalyst,wherein the silica carrier is present in an amount of from 20 to 60% byweight in terms of SiO₂, based on the total weight of the oxide catalystand the silica carrier in terms of

[0084] 13. The oxide catalyst according to item 1 above, wherein Z informula (I) is at least one element selected from the group consistingof tungsten, chromium, titanium, aluminum, tantalum, zirconium, iron,boron, indium, germanium and tin.

[0085] 14. The oxide catalyst according to item 1 above, which isproduced by a method comprising providing an aqueous raw materialmixture containing compounds of molybdenum, vanadium, antimony, niobiumand optionally Z, and drying the aqueous raw material mixture, followedby calcination.

[0086] 15. The oxide catalyst according to item 14 above, wherein thecalcination is performed at 500 to 700° C. in an atmosphere of inert gaswhich is substantially free of molecular oxygen.

[0087] 16. The oxide catalyst according to item 14 above, wherein theaqueous raw material mixture further contains oxalic acid, wherein themolar ratio of the oxalic acid to the niobium compound in terms ofniobium is in the range of from 1 to 10.

[0088] 17. A process for producing acrylonitrile or methacrylonitrile,which comprises reacting propane or isobutane with ammonia and molecularoxygen in the gaseous phase in the presence of the oxide catalyst ofitem 1 above.

[0089] 18. A process for producing acrylic acid or methacrylic acid,which comprises reacting propane or isobutane with molecular oxygen inthe gaseous phase in the presence of the oxide catalyst of item 1 above.

[0090] Hereinbelow, the present invention is described in detail.

[0091] The oxide catalyst of the present invention is for use incatalytic oxidation or ammoxidation of propane or isobutane in thegaseous phase, and comprises a composition represented by the followingformula (I):

Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I).

[0092] In formula (I), Z is at least one element selected from the groupconsisting of tungsten, chromium, titanium, aluminum, tantalum,zirconium, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel,palladium, platinum, zinc, boron, indium, germanium, tin, lead, bismuth,yttrium, gallium, rare earth elements and alkaline earth metals.

[0093] It is preferred that Z is at least one element selected from thegroup consisting of tungsten, chromium, titanium, aluminum, tantalum,zirconium, iron, boron, indium, germanium and tin. It is more preferredthat Z is at least one element selected from the group consisting oftungsten, titanium, aluminum, iron and boron.

[0094] In formula (I), a, b, c, d and n are, respectively, the atomicratios of vanadium (V), antimony (Sb), niobium (Nb), Z and oxygen (O),relative to molybdenum (Mo). Atomic ratios a, b, c and d are determinedby the charging ratios of the below-described raw material compoundsused for producing the oxide catalyst of the present invention.

[0095] In formula (I), a satisfies the relationship: 0.1≦a<0.4,preferably 0.1≦a≦0.3, more preferably 0.15≦a≦0.28. When a<0.1 or a≧0.4,the selectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

[0096] In formula (I), b satisfies the relationship: 0.1<b≦0.4,preferably 0.1<b ≦0.35, more preferably 0.2≦b≦0.33. When b≦0.1 or b>0.4,the selectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

[0097] In formula (I), c satisfies the relationship: 0.01≦c≦0.3,preferably 0.05≦c≦0.2, more preferably 0.05≦c≦0.15. When c<0.01 orc>0.3, the selectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

[0098] In formula (I), d satisfies 0≦d≦1, preferably 0≦d≦0.4, morepreferably 0.01≦d≦0.1.

[0099] When Al is used as Z element, it is preferred that d satisfiesthe relationship: 0≦d≦0.1, more advantageously 0.01≦d≦0.05.

[0100] In formula (I), a and b satisfy the relationship: a<b. When a≧b,the selectivity for (meth)acrylonitrile or (meth)acrylic acid isdisadvantageously low, or decreases with the lapse of time during thereaction.

[0101] In formula (I), n is a number determined by and consistent withthe valence requirements of the other elements present.

[0102] In an especially preferred embodiment of the present invention,a, b and c are within their respective more preferred ranges mentionedabove. Specifically, in the especially preferred embodiment of thepresent invention, a, b and c in formula (I) satisfy the followingrelationships:

[0103] 0.15≦a≦0.28;

[0104] 0.2≦b≦0.33; and

[0105] 0.05≦c≦0.15.

[0106] Further, in the especially preferred embodiment of the presentinvention, it is preferred that a, b and c not only are within theirrespective more preferred ranges mentioned above, but also satisfyspecific relationships. Specifically, it is preferred that a, b and c informula (I) satisfy the following relationships:

[0107] 0.15≦a≦0.28;

[0108] 0.2≦b≦0.33;

[0109] 0.05≦c≦0.15;

[0110] 0.5≦a+b+c≦0.69; ${\frac{a}{a + b + c} \geq 0.23};\quad {and}$${0.59 - \frac{0.528a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.7 - {\frac{0.524a}{a + b + c}.}}$

[0111] It is more preferred that a, b and c in formula (I) satisfy thefollowing relationships:

[0112] 0.16≦a≦0.28;

[0113] 0.24≦b≦0.33;

[0114] 0.07≦c≦0.15;

[0115] 0.53≦a+b+c≦0.67; ${\frac{a}{a + b + c} \geq 0.26};\quad {and}$${0.63 - \frac{0.549a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.68 - {\frac{0.529a}{a + b + c}.}}$

[0116] It is still more preferred that a, b and c in formula (I) satisfythe following relationships:

[0117] 0.16≦a≦0.26;

[0118] 0.24≦b≦0.30;

[0119] 0.08≦c≦0.12;

[0120] 0.57≦a+b+c≦0.60; ${\frac{a}{a + b + c} \geq 0.28};\quad {and}$${0.67 - \frac{0.5975a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.67 - {\frac{0.5352a}{a + b + c}.}}$

[0121] It is preferred that the oxide catalyst of the present inventionexhibits, in an X-ray diffraction pattern thereof obtained using CuK_(α)as a source of X-ray, peaks at diffraction angles (2θ) of:

[0122] 22.1±0.3°, 28.1±0.3°, 36.1±0.3° and 45.2±0.3°;

[0123] 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 35.2±0.3° and45.2±0.3°; or

[0124] 7.8±0.3°, 8.9 ±0.3°, 22.1±0.3°, 27.1±0.3°, 28.1±0.3°, 35.2±0.3°,36.1±0.3° and 45.2±0.3°.

[0125] It is especially preferred that the oxide catalyst of the presentinvention exhibits, in an X-ray diffraction pattern thereof obtainedusing CuK_(α) as a source of X-ray, peaks at diffraction angles (2θ) of7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 28.1±0.3°, 35.2±0.3°,36.1±0.3° and 45.2±0.3°.

[0126] In the present invention, the X-ray diffraction (XRD) analysis isconducted under the following conditions: Tube voltage 40 kV Tubecurrent 190 mA Divergence slit 1° Scatter slit 1° Receiving slit 0.3 mmScanning speed 5°/min. Sampling interval 0.02°

[0127] The oxide catalyst which exhibits, in an X-ray diffraction (XRD)pattern thereof, peaks at the abovementioned diffraction anglesadvantageously exhibits a high catalytic activity and a high selectivityfor the desired compound. The reason why such an oxide catalyst exhibitsa high catalytic activity and a high selectivity for the desiredcompound has not yet been elucidated. However, it is presumed that suchan oxide catalyst contains an oxide which exhibits, in an XRD patternthereof obtained using CuK_(α) as a source of X-ray, peaks atdiffraction angles (2θ) of 22.1±0.3°, 28.1±0.3°, 36.1±0.3° and45.2±0.3°; and/or an oxide which exhibits, in an XRD thereof obtainedusing CuK_(α) as a source of X-ray, peaks at diffraction angles (2θ) of7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 35.2±0.3° and 45.2±0.3°; andthat such an oxide or oxides contribute to the improvement of theperformance of the oxide catalyst.

[0128] The oxide catalyst of the present invention may exhibit, in theXRD pattern thereof, in addition to the above-mentioned peaks, a peakhaving a high intensity, as long as the performance of the oxidecatalyst is not harmfully affected.

[0129] Hereinafter, a peak appearing at a certain diffraction angle (2θ)of x±0.3° is designated as “P^(x)” (for example, a peak appearing atdiffraction angle (2θ) of 7.8±0.3° is designated as P^(7.8)).

[0130] In the present invention, it is preferred that when the intensityof P^(22.1) is taken as 100,

[0131] the intensity of P^(7.8) is from 0.5 to 30,

[0132] the intensity of P^(8.9) is from 0.5 to 30,

[0133] the intensity of P^(27.1) is from 3 to 90,

[0134] the intensity of P^(28.1) is from 10 to 300,

[0135] the intensity of P^(35.2) is from 0.5 to 30,

[0136] the intensity of P^(36.1) is from 5 to 50, and

[0137] the intensity of P^(45.2) is from 3 to 30.

[0138] The intensity of a peak appearing in an XRD pattern can beobtained as follows. For example, a method for obtaining the intensitiesof P^(27.1) and P^(28.1) is explained below referring to FIG. 2, whichis an enlarged view of the XRD pattern of FIG. 1 (XRD pattern of theoxide catalyst obtained in Example 1), showing the range of from about25° to about 30° in terms of the diffraction angle (2θ).

[0139] In FIG. 2, characters A₁ and A₂ designate the apexes of P^(27.1)and P^(28.1), respectively.

[0140] Characters B₁, B₂ and B₃ respectively designate points at whichthe curved line of the XRD pattern exhibits minimum intensity values inthe diffraction angle (2θ) ranges of 26.4±0.3°, 27.6±0.3° and 28.8±0.3°,respectively (these diffraction angle (2θ) ranges are selected to obtainan appropriate base line (i.e., line connecting B₁, B₂ and B₃) forobtaining the intensities of the peaks). In the present invention,usually, each of “the points at which the curved line of the XRD patternexhibits minimum intensity values” corresponds to a point at which thegradient of a tangential line of the curved line shifts from negative topositive, or a point at which the gradient converges to zero, whereinthe gradient is taken in the coordinates of the 2θ-axis and theintensity axis.

[0141] Character C₁ designates a point at which a line drawn downwardlyfrom peak apex A₁ vertically to the 2θ-axis intersects with a straightline connecting points B₁ and B₂.

[0142] Character C₂ designates a point at which a line drawn downwardlyfrom peak apex A₂ vertically to the 2θ-axis intersects with a straightline connecting points B₂ and B₃.

[0143] The intensity of P^(27.1) is defined as the length of straightline segment A₁C₁ which extends from peak apex A₁ (of P^(27.1)) to pointC₁; and the intensity of P^(28.1) is defined as the length of straightline segment A₂C₂ which extends from peak apex A₂ (of P^(28.1)) to pointC₂.

[0144] The intensities of other peaks appearing in the XRD pattern canbe obtained in substantially the same manner as mentioned above.Specifically, the intensities of other peaks can be obtained as follows.

[0145] The intensity of P^(7.8) is defined as the length of straightline segment A^(7.8)C^(7.8) which extends from peak apex A^(7.8) (ofP^(7.8)) to point C^(7.8), wherein the point C^(7.8) is a point at whicha line drawn downwardly from peak apex A^(7.8) vertically to the 2θ-axisintersects with a straight line connecting points B^(7.1) and B^(9.1),wherein points B^(7.1) and B^(9.1) are points at which the curved lineof the X-ray diffraction pattern exhibits minimum intensity values inthe diffraction angle (2θ) ranges of 7.1±0.3° and 9.1±0.3°,respectively.

[0146] The intensity of P^(8.9) is defined as the length of straightline segment A^(8.9)C^(8.9) which extends from peak apex A^(8.9) (ofP^(8.9)) to point C^(8.9), wherein the point C^(8.9) is a point at whicha line drawn downwardly from peak apex A^(8.9) vertically to the 2θ-axisintersects with a straight line connecting points B^(7.1) and B^(9.1),wherein points B^(7.1) and B^(9.1) are points at which the curved lineof the X-ray diffraction pattern exhibits minimum intensity values inthe diffraction angle (2θ) ranges of 7.1±0.3° and 9.1±0.3°,respectively.

[0147] The intensity of P^(22.1) is defined as the length of straightline segment A_(22.1)C^(22.1) which extends from peak apex A^(22.1) (ofP^(22.1)) to point C^(22.1), wherein the point C^(22.1) is a point atwhich a line drawn downwardly from peak apex A^(22.1) vertically to the2θ-axis intersects with a straight line connecting points B^(21.1) andB^(22.9), wherein points B^(21.1) and B^(22.9) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 21.1±0.3°and 22.9±0.3°,respectively.

[0148] The intensity of P^(35.2) is defined as the length of straightline segment A^(35.2)C^(35.2) which extends from peak apex A^(35.2) (ofP^(35.2)) to point C^(35.2), wherein the point C^(35.2) is a point atwhich a line drawn downwardly from peak apex A^(35.2) vertically to the2θ-axis intersects with a straight line connecting points B^(34.5) andB^(35.7), wherein points B^(34.5) and B^(35.7) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 34.5±0.3°and 35.7±0.3°,respectively.

[0149] The intensity of P^(36.1) is defined as the length of straightline segment A^(36.1)C^(36.1) which extends from peak apex A^(36.1) (ofP^(36.1)) to point C^(36.1), wherein the point C^(36.1) is a point atwhich a line drawn downwardly from peak apex A^(36.1) vertically to the2θ-axis intersects with a straight line connecting points B^(35.7) andB^(36.5), wherein points B^(35.7) and B^(36.5) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 35.7±0.3° and 36.5±0.3°,respectively.

[0150] The intensity of P^(45.2) is defined as the length of straightline segment A^(45.2)C^(45.2) which extends from peak apex A^(45.2) (ofP^(45.2)) to point C^(45.2), wherein the point C^(45.2) is a point atwhich a line drawn downwardly from peak apex A^(45.2) vertically to the2θ-axis intersects with a straight line connecting points B^(44.5) andB^(45.8), wherein points B^(44.5) and B^(45.8) are points at which thecurved line of the X-ray diffraction pattern exhibits minimum intensityvalues in the diffraction angle (2θ) ranges of 44.5±0.3° and 45.8±0.3°,respectively.

[0151] In the present invention, it is preferred that the intensityratio R is from 0.01 to 0.80, advantageously from 0.03 to 0.50, moreadvantageously from 0.05 to 0.20, wherein R is defined by the followingformula:

R=I^(27.1)/(I^(27.1)+I^(28.1))

[0152] wherein:

[0153] I^(27.1) represents the intensity of P^(27.1) (the peak appearingat diffraction angle (2θ) of 27.1±0.3°), and

[0154] I^(28.1) represents the intensity of P^(28.1) (the peak appearingat diffraction angle (2θ) of 28.1±0.3°).

[0155] It is preferred that the oxide catalyst of the present inventionfurther comprises a silica carrier having supported thereon said oxidecatalyst. That is, it is preferred that the oxide catalyst of thepresent invention is a silica-supported catalyst. In the presentinvention, it is preferred that the silica carrier is present in anamount of from 20 to 60% by weight, more advantageously from 25 to 55%by weight, most advantageously from 40 to 50% by weight, based on thetotal weight of the oxide catalyst and the silica carrier

[0156] The weight percentage of silica carrier is defined by thefollowing formula:

weight percentage of silica carrier=(W2/(W1+W2))×100

[0157] wherein W1 represents the weight of oxide catalyst, which iscalculated from the composition of the raw materials and the oxidationnumbers of the component elements contained in the raw materials, and W2represents the weight of silica carrier, in terms of SiO₂.

[0158] When the amount of silica carrier is less than 20% by weight,disadvantages are likely to occur wherein the strength of the oxidecatalyst becomes low, and the selectivity for and yield of(meth)acrylonitrile or (meth)acrylic acid, which are achieved by the useof the oxide catalyst, become low. On the other hand, when the amount ofsilica carrier is more than 60% by weight, the strength of the oxidecatalyst becomes high; however, the selectivity for and yield of(meth)acrylonitrile or (meth)acrylic acid, which are achieved by the useof the oxide catalyst, become low.

[0159] Next, an explanation is made below with respect to the compoundsused in the process for producing the oxide catalyst of the presentinvention as sources of the component elements of the oxide catalyst,i.e., compounds used as sources of molybdenum, vanadium, antimony,niobium, and the optional component element Z.

[0160] Examples of sources of molybdenum include ammoniumheptamolybdate, molybdenum oxides, molybdic acid, molybdenumoxychlorides, molybdenum chlorides, molybdenum alkoxides and the like.Of these, ammonium heptamolybdate is preferred.

[0161] Examples of sources of vanadium include ammonium metavanadate,vanadium (V) oxide, vanadium oxychlorides, and vanadium alkoxides. Ofthese, ammonium metavanadate and vanadium (V) oxide are preferred.

[0162] Examples of sources of antimony include antimony(III) oxide,antimony(IV) oxide, antimony(V) oxide, metantimonic acids (III),antimonic acids (V), ammonium antimonate(V), antimony(III) chloride,antimony(III) oxychloride, antimony(III) nitrate oxide, antimonyalkoxides, organic acid salts of antimony, such as antimony tartrate,and metallic antimony. Of these, antimony(III) oxide is preferred.

[0163] Examples of sources of niobium include niobic acid, niobiumoxide, niobium chloride, niobium alkoxides (such as Nb(OCH₂CH₃)₅) andorganic salts of niobium. Of these, niobic acid is preferred.

[0164] Examples of sources of Z elements include oxalic acid salts,hydroxides, oxides, nitrates, acetates, ammonium salts, carbonates andalkoxides of the Z elements.

[0165] The suitable amounts of the above-mentioned compounds as sourcesof the component elements vary depending on the types of the compoundsused, and the amounts are appropriately selected such that an oxidecatalyst having the composition represented by formula (I) is obtained.

[0166] When it is intended to use silica to obtain an oxide catalystsupported on a silica carrier, silica sol can be advantageously used asa source of silica. It is especially preferred to use a silica solstabilized with ammonium ions.

[0167] With respect to the process for producing the oxide catalyst ofthe present invention, there is no particular limitation. However, it ispreferred to produce the oxide catalyst of the present invention by aprocess comprising the following three steps: a step for providing anaqueous raw material mixture containing compounds of molybdenum,vanadium, antimony, niobium, and optionally component element Z (i.e.,step for preparing the aqueous raw material mixture), a step for dryingthe aqueous raw material mixture, and a step for calcining the resultantdried aqueous raw material mixture.

[0168] In the aqueous raw material mixture, the abovementioned compoundsused as sources of molybdenum, vanadium, antimony, niobium and theoptional component element Z may remain as they are, or may be presentin modified forms thereof which are formed by chemical reactions (e.g.,chemical reactions between the compounds used as raw materials).

[0169] Hereinbelow, explanations are made with respect to the step forproviding an aqueous raw material mixture (i.e., step for preparing theaqueous raw material mixture), the step for drying the aqueous rawmaterial mixture, and the step for calcining the resultant dried aqueousraw material mixture, wherein specific modes of the above-mentionedprocess for producing the oxide catalyst of the present invention aretaken as examples.

[0170] <Aqueous Raw Material Mixture Preparation Step>

[0171] An aqueous mixture containing ammonium heptamolybdate, ammoniummetavanadate and antimony(III) oxide is subjected to a reaction,preferably, at 70 to 100° C., while stirring for 1 to 5 hours. Theresultant mixture containing molybdenum, vanadium and antimony issubjected to an oxidation by air or an oxidation in a liquid phase byusing hydrogen peroxide or the like, to thereby obtain an aqueousmixture (A). It is preferred that the oxidation is conducted to anextent wherein the change in color of the aqueous mixture from dark blueto orange or brown is visually observed. In the case where the oxidationis conducted in a liquid phase by using hydrogen peroxide, the molarratio of hydrogen peroxide to antimony is preferably 0.5 to 2. Themolybdenum concentration of the aqueous mixture (A) is preferably 0.2mol/kg or more, more preferably 0.5 mol/kg or more.

[0172] Alternatively, to an aqueous solution having ammoniumheptamolybdate dissolved therein are added antimony(III) oxide andaqueous hydrogen peroxide having a hydrogen peroxide concentration of0.01 to 30% by weight (preferably 0.1 to 10% by weight), followed bystirring at 50 to 80° C. The molar ratio of hydrogen peroxide toantimony is preferably 0.5 to 5. To the resultant aqueous solution isadded ammonium metavanadate to obtain an aqueous mixture (A′). Themolybdenum concentration of the aqueous mixture (A′) is preferably 0.2mol/kg or more, more preferably 0.5 mol/kg or more.

[0173] On the other hand, a niobium-containing aqueous mixture (B) isprepared by dissolving a niobic acid in an aqueous oxalic acid solution.The niobium concentration of the niobium-containing aqueous mixture (B)is preferably 0.05 mol/kg or more, more preferably 0.15 mol/kg or more.The oxalic acid/niobium molar ratio in the niobium-containing aqueousmixture (B) is preferably in the range of from 1 to 10, more preferablyfrom 2 to 6, most preferably from 2 to 4. For obtaining theabove-mentioned preferred oxide catalyst which exhibits, in the X-raydiffraction pattern, peaks at specific diffraction angles, it isespecially preferred that the oxalic acid/niobium molar ratio is in therange of from 2 to 4. However, when, prior to the below-describedcalcination step, pre-calcination is performed, the above-mentionedpreferred oxide catalyst can be obtained even if the oxalic acid/niobiummolar ratio is not in the range of from 2 to 4, but the molar ratio ispreferably in the range of from 1 to 10.

[0174] To the obtained niobium-containing aqueous mixture (B) may beadded aqueous hydrogen peroxide. The addition of aqueous hydrogenperoxide enables the improvement of performance of the oxide catalyst,that is, it becomes possible to improve the space time yield and theselectivity for the desired compound in a catalytic oxidation orammoxidation of propane or isobutane in the gaseous phase. When aqueoushydrogen peroxide is added to the niobium-containing aqueous mixture(B), the molar ratio of hydrogen peroxide to niobic acid (in terms ofniobium atoms) is preferably in the range of from 0.5 to 10, morepreferably from 2 to 6.

[0175] By mixing the thus obtained aqueous mixture (A) or (A′) with thethus obtained niobium-containing aqueous mixture (B), the aqueous rawmaterial mixture can be obtained. The obtained aqueous raw materialmixture is subjected to the below-described drying step.

[0176] When it is intended to produce an oxide catalyst supported on asilica carrier, a silica sol may be added at any time during theabove-descried procedures to thereby obtain a silica sol-containingaqueous raw material mixture, and the obtained silica sol-containingaqueous raw material mixture is subjected to the below-described dryingstep.

[0177] When it is intended to produce an oxide catalyst containing the Zelement which is an optional component, a compound containing the Zelement may be added at any time during the above-descried procedures tothereby obtain a Z element-containing aqueous raw material mixture, andthe obtained Z element-containing aqueous raw material mixture issubjected to the below-described drying step.

[0178] <Drying Step>

[0179] The above-obtained aqueous raw material mixture is dried by spraydrying or evaporation drying to thereby obtain a dried powder. The spraydrying can be conducted by centrifugation, by two-phase flow nozzlemethod or by high pressure nozzle method. As a heat source for drying,it is preferred to use air which has been heated by steam, an electricheater and the like. It is preferred that the temperature of the heatedair at an entrance to the dryer section thereof is from 150 to 300° C.The spray drying can be also conveniently conducted by spraying theaqueous raw material mixture onto an iron plate which has been heated toa temperature of 100 to 300° C.

[0180] For obtaining the above-mentioned preferred oxide catalyst whichexhibits, in the X-ray diffraction pattern, peaks at specificdiffraction angles, it is especially preferred to conduct the dryingstep by spray drying.

[0181] <Calcination Step>

[0182] In the calcination step, the dried powder obtained in the dryingstep is calcined so as to obtain the oxide catalyst of the presentinvention. The calcination can be conducted by using a kiln, such as arotary kiln, a tunnel kiln, a muffle kiln or a fluidized-bed kiln. Thecalcination is conducted in an atmosphere of an inert gas, such asnitrogen gas which is substantially free of oxygen, or alternatively, inan atmosphere containing an oxidative gas (such as an oxygen-containinggas) in combination with a reductive gas (such as a gaseous organiccompound (e.g., propane or isobutane) or gaseous ammonia). Thecalcination is preferably conducted in an atmosphere of an inert gas,such as nitrogen gas which is substantially free of oxygen, morepreferably under a flow of an inert gas, at a temperature of 400 to 700°C., preferably 570 to 670° C. The time of calcination is generally 0.5to 10 hours, preferably 1 to 3 hours. It is preferred that the oxygenconcentration of the above-mentioned inert gas is 1000 ppm or less, moreadvantageously 100 ppm or less, most advantageously 10 ppm or less, asmeasured by gas chromatography or by means of a trace oxygen analyzer.The calcination can be conducted repeatedly. Prior to the calcination,the dried powder may be subjected to pre-calcination in an atmosphere ofair or under a stream of air at 200 to 420° C., preferably 250 to 350°C. for 10 minutes to 5 hours. The catalyst obtained by calcination maybe subjected to further calcination in an atmosphere of air at atemperature of from 200 to 400° C. for 5 minutes to 5 hours.

[0183] The thus produced oxide catalyst of the present invention can beused as a catalyst for producing (meth)acrylonitrile by ammoxidation ofpropane or isobutane in the gaseous phase. The oxide catalyst of thepresent invention can also be used as a catalyst for producing(meth)acrylic acid by oxidation of propane or isobutane in the gaseousphase. The oxide catalyst of the present invention is preferably used asa catalyst for producing (meth)acrylonitrile, more preferably as acatalyst for producing acrylonitrile.

[0184] Propane or isobutane used for producing (meth)acrylic acid, andpropane or isobutane and ammonia used for producing (meth)acrylonitrileneed not be of very high purity but may be of a commercial grade.

[0185] Examples of sources of molecular oxygen fed into the reactionsystem include air, oxygen-rich air, and pure oxygen. Further, such asource of molecular oxygen may be diluted with steam, helium, argon,carbon dioxide, nitrogen or the like.

[0186] In the case of an ammoxidation reaction in the gaseous phase, themolar ratio of ammonia to propane or isobutane for the ammoxidation isgenerally in the range of from 0.1 to 1.5, preferably from 0.2 to 1.2.When the ammoxidation is performed in a recycling mode, the molar ratioof ammonia to propane or isobutane at the entrance of a reactor used ispreferably in the range of from 0.2 to 1.0, more preferably from 0.5 to0.8.

[0187] The molar ratio of molecular oxygen to propane or isobutane usedfor the ammoxidation is preferably in the range of from 0.2 to 6, morepreferably from 0.4 to 4. When the ammoxidation is performed in arecycling mode, it is preferred that the molar ratio of molecular oxygento propane or isobutane at the entrance of the reactor used ispreferably in the range of 0.8 to 2.2, more preferably from 1.5 to 1.9.

[0188] In the case of an oxidation reaction in the gaseous phase, themolar ratio of molecular oxygen to propane or isobutane used for theoxidation is generally in the range of from 0.1 to 10, preferably from0.1 to 5. It is preferred that steam is introduced into the reactionsystem. The molar ratio of steam to propane or isobutane used for theoxidation is generally in the range of from 0.1 to 70, preferably from 3to 40.

[0189] In each of the ammoxidation reaction in the gaseous phase and theoxidation reaction in the gaseous phase, the reaction pressure isgenerally in the range of from 0.01 to 1 MPa, preferably from 0.1 to 0.3MPa, in terms of the absolute pressure.

[0190] In the ammoxidation reaction in the gaseous phase, the reactiontemperature is generally in the range of from 300 to 600° C., preferablyfrom 380 to 470° C.

[0191] In the oxidation reaction in the gaseous phase, the reactiontemperature is generally in the range of from 300 to 600° C., preferablyfrom 350 to 440° C.

[0192] In each of the ammoxidation reaction in the gaseous phase and theoxidation reaction in the gaseous phase, the time of contact (contacttime) between gaseous feedstocks (containing propane or isobutane,molecular oxygen and the like) and the catalyst is generally in therange of from 0.1 to 30 (g·sec/ml), preferably from 0.5 to 10(g·sec/ml). In the present invention, the contact time is determinedaccording to the following formula:${{Contact}\quad {{time}\left( {g \cdot {\sec/{ml}}} \right)}} = {\frac{W}{F} \times 60 \times \frac{273}{273 + T} \times \frac{P + 0.101}{0.101}}$

[0193] wherein:

[0194] W represents the weight (g) of the oxide catalyst contained inthe reactor;

[0195] F represents the flow rate (ml/min) of the gaseous feed stocks;

[0196] T represents the reaction temperature (° C.); and

[0197] P represents the reaction pressure (MPa) (gauge pressure).

[0198] Each of the ammoxidation reaction in the gaseous phase and theoxidation reaction in the gaseous phase can be conducted in aconventional reactor, such as a fixed bed reactor, a fluidized-bedreactor or a moving bed reactor, preferably in a fluidized-bed reactor.The reaction mode may be either a one pass mode or a recycling mode. Ofthese two reaction modes, a recycling mode is preferred.

BEST MODE FOR CARRYING OUT THE INVENTION

[0199] Hereinbelow, the present invention will be described in moredetail with reference to the following Examples and ComparativeExamples, which should not be construed as limiting the scope of thepresent invention.

[0200] (1) Conversion of Propane, Selectivity for Acrylonitrile andSelectivity for Acrylic Acid:

[0201] In the following Examples and Comparative Examples, the resultsof the oxidation or ammoxidation were evaluated in terms of theconversion (%) of propane, the selectivity (%) for acrylonitrile and theselectivity (%) for acrylic acid, which are, respectively, defined asfollows:${{Conversion}\quad (\%)\quad {of}\quad {propane}} = {\frac{{mole}\quad {of}\quad {propane}\quad {reacted}}{{mole}\quad {of}\quad {propane}\quad {fed}} \times 100}$${{Selectivity}\quad (\%)\quad {for}\quad {acrylonitrile}} = {\frac{\begin{matrix}{{mole}\quad {of}\quad {acrylonitrile}} \\{formed}\end{matrix}}{\begin{matrix}{{mole}\quad {of}\quad {propane}} \\{reacted}\end{matrix}} \times 100}$${{Selectivity}\quad (\%)\quad {for}\quad {acrylic}\quad {acid}} = {\frac{\begin{matrix}{{mole}\quad {of}\quad {acrylic}} \\{{acid}\quad {formed}}\end{matrix}}{\begin{matrix}{{mole}\quad {of}\quad {propane}} \\{reacted}\end{matrix}} \times 100}$

[0202] (2) X-Ray Diffractometry of Oxide Catalyst:

[0203] An X-ray diffraction (XRD) pattern of the oxide catalyst wasobtained by subjecting the oxide catalyst to measurement by X-raydiffractometry using an X-ray diffractometer MXP-18 (manufactured andsold by MAC Science Ltd., Japan). The method for preparing a sample andXRD pattern measurement conditions are as follows.

[0204] <Preparation of a Sample>

[0205] About 0.5 g of the catalyst was placed in an agate mortar andsubjected to grinding for 2 minutes by manually operating an agatepestle. The resultant catalyst powder was subjected to sifting, tothereby obtain a powdery catalyst having a particle size of 53 μm orless. The obtained powdery catalyst was placed on a sample-holding tablefor an XRD pattern measurement. The table had a rectangular recess inthe surface thereof (which has the following dimensions: a length of 20mm, a width of 16 mm and a depth of 0.2 mm), and the powdery catalyst inthe recess was pressed using a stainless steel spatula having a flatshape so that the surface of the powdery catalyst became flat.

[0206] <XRD Pattern Measurement Conditions>

[0207] An XRD pattern measurement was conducted under the followingconditions. Source of X-ray CuK_(α1) + CuK_(α2) Detector Scintillationcounter Single crystal Graphite used for a monochromator Tube voltage 40kV Tube current 190 mA Divergence slit 1° Scatter slit 1° Receiving slit0.3 mm Scanning speed 5°/min. Sampling interval 0.02° Scanning method2θ/θ method

[0208] The diffraction angle (2θ) correction was conducted by performinga calibration using X-ray diffractometry data obtained with respect to asilicon powder. Further, a smoothing treatment of the XRD pattern wasperformed.

[0209] With respect to the obtained XRD pattern, the intensity ratio Ris defined by the following formula:

R=I^(27.1)/(I^(27.1)+I^(28.1))

[0210] wherein:

[0211] I^(27.1) represents the intensity of P^(27.1) (the peak appearingat diffraction angle (2θ) of 27.1±0.3°), and

[0212] I^(28.1) represents the intensity of P^(28.1) (the peak appearingat diffraction angle (2θ) 28.1±0.3°).

EXAMPLE 1

[0213] (Preparation of a Catalyst)

[0214] An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0215] To 1,000 g of water were added 250 g of ammonium heptamolybdate[(NH₄)₆Mo₇O₂₄.4H₂O], 38.1 g of ammonium metavanadate (NH₄VO₃) and 53.6 gof antimony(III) oxide (Sb₂O₃), and the resultant mixture was subjectedto a reaction under reflux in an oil bath in the air at 100° C. for 2hours, followed by cooling to 50° C. Subsequently, to the resultantreaction mixture was added 829 g of a silica sol having an SiO₂ contentof 30% by weight, followed by stirring for 30 minute. Then, to theresultant mixture was further added 250 g of 5 wt % aqueous hydrogenperoxide, and the resultant mixture was stirred at 50° C. for 1 hour toeffect an oxidation treatment, to thereby obtain an aqueous mixture (A).By the oxidation treatment, the color of the mixture changed from darkblue to brown.

[0216] On the other hand, to 150 g of water were added 22.3 g of niobicacid (Nb₂O₅ content: 76% by weight) and 43.4 g of oxalic acid dehydrate(H₂C₂O₄.2H₂O), and the resultant mixture was heated at 60° C. whilestirring to dissolve the niobic acid and oxalic acid dihydrate in thewater, followed by cooling to 30° C., to thereby obtain an aqueousniobium-oxalic acid solution (B).

[0217] The thus obtained aqueous niobium-oxalic acid solution (B) wasadded to the above-prepared aqueous mixture (A), and the resultantmixture was stirred at 50° C. for 30 minutes in the air, to therebyobtain an aqueous raw material mixture.

[0218] The obtained aqueous raw material mixture was subjected to aspray drying by means of a centrifugation type spray-drying apparatusunder conditions wherein the entrance and exit temperatures of the dryerof the spray-drying apparatus were 230° C. and 120° C., respectively, tothereby obtain a dried powder comprised of spherical particles. 100 g ofthe obtained dried powder was charged into a quartz container andcalcined in a kiln at 640° C. for 2 hours under a flow of nitrogen gasat a flow rate of 600 Nml/min. (Nml means ml as measured under thenormal temperature and pressure conditions, namely, at 0° C. under 1atm.) while rotating the quartz container, to thereby obtain an oxidecatalyst. The oxygen concentration of the nitrogen gas used for thecalcination was determined by means of a trace oxygen analyzer (Model306WA, manufactured and sold by Teledyne Analytical Instruments,U.S.A.), and it was found that the oxygen concentration of the nitrogengas was 1 ppm.

[0219] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0220] With respect to the obtained oxide catalyst, the X-raydiffraction (XRD) pattern obtained using CuK_(α) as a source of X-ray isshown in FIG. 1.

[0221] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.08.

[0222] (Ammoxidation of Propane)

[0223] 0.35 g of the obtained oxide catalyst (W=0.35 g) was charged intoa fixed-bed type reaction tube having an inner diameter of 4 mm. Agaseous feedstock mixture having a molar ratio ofpropane:ammonia:oxygen:helium of 1:0.7:1.7:5.3 was fed into the reactiontube at a flow rate (F) of 3.6 (ml/min). The reaction temperature (T)(external temperature) was 420° C. and the reaction pressure (P) was 0MPa in terms of the gauge pressure. The contact time between the oxidecatalyst and the gaseous mixture of the feedstocks was 2.3 (g·sec/ml).The contact time was obtained by the following formula:${{Contact}\quad {time}} = {\frac{W}{F} \times 60 \times \frac{273}{273 + T} \times \frac{P + 0.101}{0.101}}$

[0224] The produced gaseous reaction mixture was analyzed by means of anon-line gas chromatography apparatus. The results are shown in Table 1.

EXAMPLE 2

[0225] (Preparation of a Catalyst)

[0226] An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)n/SiO₂(45% by weight) was prepared asfollows.

[0227] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that the amount of antimony(III)oxide (Sb₂O₃) was changed from 53.6 g to 51.6 g, the amount of 5 wt %aqueous hydrogen peroxide was changed from 250 g to 241 g and the amountof silica sol was changed from 829 g to 823 g.

[0228] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0229] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.09.

[0230] (Ammoxidation of Propane)

[0231] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in the same manner as in Example 1. The resultsare shown in Table 1.

EXAMPLE 3

[0232] (Preparation of a Catalyst)

[0233] An oxide catalyst represented by the formula:Mo₁V_(0.24)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂ (45% by weight) was prepared asfollows.

[0234] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that the amount of ammoniummetavanadate (NH₄VO₃) was changed from 38.1 g to 39.7 g, the amount ofantimony(III) oxide (Sb₂O₃) was changed from 53.6 g to 51.6 g, theamount of 5 wt % aqueous hydrogen peroxide was changed from 250 g to 241g and the amount of silica sol was changed from 829 g to 827 g.

[0235] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0236] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.09.

[0237] (Ammoxidation of Propane)

[0238] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in the same manner as in Example 1. The resultsare shown in Table 1.

EXAMPLE 4

[0239] (Preparation of a Catalyst)

[0240] An oxide catalyst represented by the formula:Mo₁V_(0.24)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0241] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that the amount of ammoniummetavanadate (NH₄VO₃) was changed from 38.1 g to 39.7 and the amount ofsilica sol was changed from 829 g to 833 g.

[0242] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0243] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.10.

[0244] (Ammoxidation of Propane)

[0245] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in the same manner as in Example 1. The resultsare shown in Table 1.

EXAMPLE 5

[0246] (Preparation of a Catalyst)

[0247] An oxide catalyst represented by the formula:Mo₁V_(0.25)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0248] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that the amount of ammoniummetavanadate (NH₄VO₃) was changed from 38.1 g to 41.4 g and the amountof silica sol was changed from 829 g to 836 g.

[0249] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0250] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.10.

[0251] (Ammoxidation of Propane)

[0252] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in the same manner as in Example 1. The resultsare shown in Table 1.

EXAMPLE 6

[0253] (Preparation of a Catalyst)

[0254] An oxide catalyst represented by the formula:Mo₁V_(0.20)Sb_(0.29)Nb_(0.11)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0255] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0256] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate (NH₄VO₃) was changed from 38.1 g to 33.1 g, the amount ofantimony(III) oxide (Sb₂O₃) was changed from 53.6 g to 59.8 g, theamount of 5 wt % aqueous hydrogen peroxide was changed from 250 g to 279g and the amount of silica sol was changed from 829 g to 846 g; and

[0257] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 180 g, the amount ofniobic acid was changed from 22.3 g to 27.2 g and the amount of oxalicacid dihydrate was changed from 43.4 g to 53.0 g.

[0258] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0259] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.14.

[0260] (Ammoxidation of Propane)

[0261] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 3.3 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 2.5 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 7

[0262] (Preparation of a Catalyst)

[0263] An oxide catalyst represented by the formula:Mo₁V_(0.22)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0264] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that the amount of ammoniummetavanadate (NH₄VO₃) was changed from 38.1 g to 36.4 g and the amountof silica sol was changed from 829 g to 825 g.

[0265] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0266] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.08.

[0267] (Ammoxidation of Propane)

[0268] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in the same manner as in Example 1. The resultsare shown in Table 1.

EXAMPLE 8

[0269] (Preparation of a catalyst)

[0270] An oxide catalyst represented by the formula:Mo₁V_(0.22)Sb_(0.27)Nb_(0.10)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0271] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0272] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 36.4 g, the amount ofantimony(III) oxide was changed from 53.6 g to 55.7 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 260 g and theamount of silica sol was changed from 829 g to 836 g; and

[0273] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 165 g, the amount ofniobic acid was changed from 22.3 g to 24.7 g and the amount of oxalicacid dihydrate was changed from 43.4 g to 48.2 g.

[0274] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0275] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.12.

[0276] (Ammoxidation of Propane)

[0277] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 3.4 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 2.4 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 9

[0278] (Preparation of a Catalyst)

[0279] An oxide catalyst represented by the formula:Mo₁V_(0.17)Sb_(0.30)Nb_(0.12)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0280] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0281] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 28.2 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 846 g; and

[0282] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 200 g, the amount ofniobic acid was changed from 22.3 g to 29.7 g and the amount of oxalicacid dihydrate was changed from 43.4 g to 57.8 g.

[0283] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0284] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.16.

[0285] (Ammoxidation of Propane)

[0286] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 3.2 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 2.6 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 10

[0287] (Preparation of a Catalyst)

[0288] An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂(40% by weight) was prepared asfollows.

[0289] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that the amount of antimony(III)oxide (Sb₂O₃) was changed from 53.6 g to 51.6 g, the amount of 5 wt %aqueous hydrogen peroxide was changed from 250 g to 241 g and the amountof silica sol was changed from 829 g to 671 g.

[0290] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0291] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.10.

[0292] (Ammoxidation of Propane)

[0293] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 4.0 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 2.1 (g·sec/ml). The results are shown in Table 1.

EXAMPLE 11

[0294] (Preparation of a Catalyst)

[0295] An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0296] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that 173 g of 5 wt % aqueoushydrogen peroxide was further added to aqueous niobium-oxalic acidsolution (B).

[0297] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 1.

[0298] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.08.

[0299] (Ammoxidation of Propane)

[0300] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 4.7 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 1.7 (g·sec/ml). The results are shown in Table 1.

COMPARATIVE EXAMPLE 1

[0301] (Preparation of a catalyst)

[0302] An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0303] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0304] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 47.5 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 221 g and theamount of silica sol was changed from 829 g to 826 g; and

[0305] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 116 g, the amount ofniobic acid was changed from 22.3 g to 17.3 g and the amount of oxalicacid dihydrate was changed from 43.4 g to 33.7 g.

[0306] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 2.

[0307] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.18.

[0308] (Ammoxidation of Propane)

[0309] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1.The results are shown in Table 2.

COMPARATIVE EXAMPLE 2

[0310] (Preparation of a Catalyst)

[0311] An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.15)Nb_(0.05)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0312] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0313] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 30.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 144 g and theamount of silica sol was changed from 829 g to 771 g; and

[0314] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 83 g, the amount of niobicacid was changed from 22.3 g to 12.4 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 24.1 g.

[0315] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 2.

[0316] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.10.

[0317] (Ammoxidation of Propane)

[0318] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 3.7 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 2.2 (g·sec/ml). The results are shown in Table 2.

COMPARATIVE EXAMPLE 3

[0319] (Preparation of a Catalyst)

[0320] An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.20)Nb_(0.05)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0321] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0322] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 41.3 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 192 g and theamount of silica sol was changed from 829 g to 800 g; and

[0323] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 83 g, the amount of niobicacid was changed from 22.3 g to 12.4 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 24.1 g.

[0324] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 2.

[0325] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.12.

[0326] (Ammoxidation of Propane)

[0327] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1.The results are shown in Table 2.

COMPARATIVE EXAMPLE 4

[0328] (Preparation of a Catalyst)

[0329] An oxide catalyst represented by the formula:Mo₁V_(0.25)Sb_(0.5)Nb_(0.125)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0330] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0331] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 41.4 g, the amount ofantimony(III) oxide was changed from 53.6 g to 103.2 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 481 g and theamount of silica sol was changed from 829 g to 989 g; and

[0332] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 210 g, the amount ofniobic acid was changed from 22.3 g to 30.9 g and the amount of oxalicacid dihydrate was changed from 43.4 g to 60.3 g.

[0333] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 2.

[0334] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 22.1±0.3°, 28.1±0.3°, 36.1±0.3° and45.2±0.3°, but not at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°,27.1±0.3° and 35.2±0.3°.

[0335] (Ammoxidation of Propane)

[0336] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 2.0 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 4.2 (g·sec/ml). The results are shown in Table 2.

COMPARATIVE EXAMPLE 5

[0337] (Preparation of a Catalyst)

[0338] An oxide catalyst represented by the formula:Mo₁V_(0.3)Sb_(0.3)Nb_(0.1)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0339] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0340] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 881 g; and

[0341] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 166 g, the amount ofniobic acid was changed from 22.3 g to 24.7 g and the amount of oxalicacid dihydrate was changed from 43.4 g to 48.2 g.

[0342] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 2.

[0343] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.06.

[0344] (Ammoxidation of Propane)

[0345] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1.The results are shown in Table 2.

COMPARATIVE EXAMPLE 6

[0346] (Preparation of a Catalyst)

[0347] An oxide catalyst represented by the formula:Mo₁V_(0.3)Sb_(0.3)Nb_(0.05)O_(n)/SiO₂(45% by weight) was prepared asfollows.

[0348] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0349] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 855 g; and

[0350] in the preparation of aqueous niobium-oxalic acid solution (B),the amount of water was changed from 150 g to 84 g, the amount of niobicacid was changed from 22.3 g to 12.4 g and the amount of oxalic aciddihydrate was changed from 43.4 g to 24.1 g.

[0351] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 2.

[0352] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8+0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3 °, 36.1±0.3° and 45.2±0.3°, whereinR=0.12.

[0353] (Ammoxidation of Propane)

[0354] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 2.0 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 4.2 (g·sec/ml). The results are shown in Table 2.

COMPARATIVE EXAMPLE 7

[0355] (Preparation of a Catalyst)

[0356] An oxide catalyst represented by the formula:Mo₁V_(0.3)Sb_(0.3)O_(n)/SiO₂(45% by weight) was prepared as follows.

[0357] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that:

[0358] in the preparation of aqueous mixture (A), the amount of ammoniummetavanadate was changed from 38.1 g to 49.7 g, the amount ofantimony(III) oxide was changed from 53.6 g to 61.9 g, the amount of 5wt % aqueous hydrogen peroxide was changed from 250 g to 289 g and theamount of silica sol was changed from 829 g to 830 g; and

[0359] aqueous niobium-oxalic acid solution (B) was not used.

[0360] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 2.

[0361] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 22.1±0.3°, 27.1±0.3°, 28.1±0.3°,35.2±0.3°, 36.1±0.3° and 45.2±0.3°, but not at diffraction angles (2θ)of 7.8±0.3° and 8.9±0.3°.

[0362] (Ammoxidation of Propane)

[0363] Using the obtained oxide catalyst, the ammoxidation reaction ofpropane was performed in substantially the same manner as in Example 1,except that flow rate (F) of the gaseous feedstock mixture was changedfrom 3.6 (ml/min) to 2.0 (ml/min) and the contact time was changed from2.3 (g·sec/ml) to 4.2 (g·sec/ml). The results are shown in Table 2.TABLE 1 Ammoxidation of propane^((*2)) Selec- Conditions of the Conver-tivity catalyst production sion for process^((*1)) Contact of acrylo-H₂C₂O₄/ H₂O₂/ H₂O₂/ time propane nitrile Composition Nb Sb Nb (S) (%)(%) Ex. 1 Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.348.5 66.4 Ex. 2 Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 1 02.3 48.4 66.4 Ex. 3 Mo₁V_(0.24)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.71 0 2.3 48.6 66.1 Ex. 4 Mo₁V_(0.24)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45 wt %)2.7 1 0 2.3 48.2 66.2 Ex. 5 Mo₁V_(0.25)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45wt %) 2.7 1 0 2.3 48.1 66.0 Ex. 6Mo₁V_(0.20)Sb_(0.29)Nb_(0.11)O_(n)/SiO₂(45 Wt %) 2.7 1 0 2.5 48.9 64.8Ex. 7 Mo₁V_(0.22)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.3 48.765.8 Ex. 8 Mo₁V_(0.22)Sb_(0.27)Nb_(0.10)O_(n)/SiO₂(45 wt %) 2.7 1 0 2.448.7 65.5 Ex. 9 Mo₁V_(0.17)Sb_(0.30)Nb_(0.12)O_(n)/SiO₂(45 wt %) 2.7 1 02.6 48.2 64.8 Ex. 10 Mo₁V_(0.23)Sb_(0.25)Nb_(0.09)O_(n)/SiO₂(40 wt %)2.7 1 0 2.1 49.0 66.8 Ex. 11 Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(45Wt %) 2.7 1 2 1.7 49.5 68.0

[0364] TABLE 2 Ammoxidation of propane⁽*²⁾ Conditions of the Selectivitycatalyst production Conversion for process⁽*¹⁾ Contact of acrylo-H₂C₂O₄/ H₂O₂/ H₂O₂/ time propane nitrile Composition Nb Sb Nb (S) (%)(%) Com. Ex. 1 Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂ (45 wt %) 2.7 1 02.3 48.3 63.3 Com. Ex. 2 Mo₁V_(0.30)Sb_(0.15)Nb_(0.05)O_(n)/SiO₂ (45 wt%) 2.7 1 0 2.2 48.8 61.3 Com. Ex. 3Mo₁V_(0.30)Sb_(0.20)Nb_(0.05)O_(n)/SiO₂ (45 wt %) 2.7 1 0 2.3 48.6 62.8Com. Ex. 4 Mo₁V_(0.25)Sb_(0.5)Nb_(0.125)O_(n)/SiO₂ (45 wt %) 2.7 1 0 4.29.0 23.0 Com. Ex. 5 Mo₁V_(0.3)Sb_(0.3)Nb_(0.1)O_(n)/SiO₂ (45 wt %) 2.7 10 2.3 40.0 53.0 Com. Ex. 6 Mo₁V_(0.3)Sb_(0.3)Nb_(0.05)O_(n)/SiO₂ (45 wt%) 2.7 1 0 4.2 34.0 49.1 Com. Ex. 7 Mo₁V_(0.3)Sb_(0.3)O_(n)/SiO₂ (45 wt%) 2.7 1 0 4.2 4.5 5.2

EXAMPLE 12

[0365] (Ammoxidation of Propane)

[0366] 30 g of the oxide catalyst obtained in Example 1 was charged intoa Vycor glass fluidized-bed reaction tube having an inner diameter of 25mm. A gaseous feedstock mixture having a molar ratio ofpropane:ammonia:molecular oxygen:helium of 1:0.70:1.68:5.32 was fed intothe reaction tube at a flow rate of 420 (ml/min). The reactiontemperature was 440° C. (internal temperature), the reaction pressurewas 0.049 MPa in terms of the gauge pressure, and the contact time was2.4 (g·sec/ml).

[0367] 24 Hours, 240 hours, 400 hours and 1000 hours after the start ofthe reaction, the produced gaseous reaction mixture was analyzed bymeans of an on-line gas chromatography apparatus. The results are shownin Table 3.

EXAMPLE 13

[0368] The ammoxidation reaction of propane was performed insubstantially the same manner as in Example 12, except that 30 g of theoxide catalyst obtained in Example 1 was changed to 25 g of the oxidecatalyst obtained in Example 11, the flow rate (F) of the gaseousfeedstock mixture was changed from 420 (ml/min) to 460 (ml/min) and thecontact time was changed from 2.4 (g·sec/ml) to 1.8 (g·sec/ml). Theresults are shown in Table 3.

[0369] As apparent from the results of Examples 12 and 13, by the use ofthe oxide catalyst of the present invention, even in the continuouscatalytic ammoxidation of propane in the gaseous phase using a gaseousfeedstock mixture having a high partial pressure of propane, theselectivity for the desired product (i.e., acrylonitrile) is maintainedat a high level for a long time.

COMPARATIVE EXAMPLE 8

[0370] The ammoxidation reaction of propane was performed insubstantially the same manner as in Example 12, except that 30 g of theoxide catalyst obtained in Example 1 was changed to 30 g of the oxidecatalyst obtained in the Comparative Example 1 (which exhibits, in theammoxidation reaction of propane, the highest selectivity foracrylonitrile among the oxide catalysts obtained in ComparativeExamples)) and the contact time was changed from 2.4 (g·sec/ml) to 2.8(g·sec/ml).

[0371] Since the oxide catalyst used was found to be deteriorated withthe lapse of time, the flow rate (F) of the gaseous feedstock mixturewas appropriately controlled such that the conversion of propane wasmaintained at approximately 50%. 240 Hours after the start of thereaction, the flow rate was 380 (ml/min). 400 Hours after the start ofthe reaction, the flow rate was 360 (ml/min).

[0372] However, since the selectivity for acrylonitrile was markedlylowered, the reaction was terminated 400 hours after the start of thereaction. The results are shown in Table 3. TABLE 3 Ammoxidation ofpropane⁽*¹⁾ 24 hours after the start 240 hours after the start 400 hoursafter the start 1000 hours after the start of the reaction of thereaction of the reaction of the reaction Selectivity SelectivitySelectivity Selectivity Conversion for Conversion for Conversion forConversion for of acrylo- of acrylo- of acrylo- of acrylo- propanenitrile propane nitrile propane nitrile propane nitrile Composition (%)(%) (%) (%) (%) (%) (%) (%) Ex. 12 Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/50.2 60.1 50.0 59.6 50.0 59.7 49.9 59.7 SiO₂ (45 wt %) Ex. 13Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/ 50.1 61.8 50.2 61.4 50.0 61.4 49.861.4 SiO₂ (45 wt %) Comp. Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/ 50.0 57.650.0 54.5 50.0 52.7 Ex. 8 SiO₂(45 wt %)

EXAMPLE 14

[0373] (Preparation of a Catalyst)

[0374] An oxide catalyst represented by the formula:Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂(41% by weight) was prepared asfollows.

[0375] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Example 1, except that the amount of the silicasol was changed from 829 g to 704 g.

[0376] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 4.

[0377] The obtained oxide catalyst exhibits, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3 , 22.1±0.3 ,27.1±0.3 , 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.08.

[0378] (Oxidation of Propane)

[0379] 0.35 g of the obtained oxide catalyst (W=0.35 g) was charged intoa fixed-bed type reaction tube having an inner diameter of 4 mm. Agaseous feedstock mixture having a molar ratio of propane:molecularoxygen:steam:helium of 1:3:14:10 was fed into the reaction tube at aflow rate (F) of 4.5 (ml/min). The reaction temperature (T) was 380° C.(external temperature) and the reaction pressure (P) was 0 MPa in termsof the gauge pressure. The contact time was 2.0 (g·sec/ml).

[0380] The produced gaseous reaction mixture was analyzed by means of agas chromatography apparatus. The results are shown in Table 4.

COMPARATIVE EXAMPLE 9

[0381] (Preparation of a Catalyst)

[0382] An oxide catalyst represented by the formula:Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂ (41% by weight) was prepared asfollows.

[0383] Preparation of an oxide catalyst was performed in substantiallythe same manner as in Comparative Example 1, except that the amount ofthe silica sol was changed from 829 g to 702 g.

[0384] The composition of the oxide catalyst and the importantconditions in the catalyst production process are shown in Table 4.

[0385] The obtained oxide catalyst exhibited, in an XRD pattern thereof,peaks at diffraction angles (2θ) of 7.8±0.3°, 8.9±0.3°, 22.1±0.3°,27.1±0.3°, 28.1±0.3°, 35.2±0.3°, 36.1±0.3° and 45.2±0.3°, whereinR=0.18.

[0386] (Oxidation of Propane)

[0387] Using the obtained oxide catalyst, the oxidation of propane wasperformed in substantially the same manner as in Example 14. The resultsare shown in Table 4. TABLE 4 Ammoxidation of propane⁽*²⁾ Conditions ofthe Selectivity catalyst production Conversion for process⁽*¹) Contactof acrylo- H₂C₂O₄/ H₂O₂/ H₂O₂/ time propane nitrile Composition Nb Sb Nb(S) (%) (%) Ex. 14 Mo₁V_(0.23)Sb_(0.26)Nb_(0.09)O_(n)/SiO₂ (41 wt %) 2.71 0 2.0 63.8 51.5 Com. Ex. 9 Mo₁V_(0.30)Sb_(0.23)Nb_(0.07)O_(n)/SiO₂ (41wt %) 2.7 1 0 2.0 63.5 48.1

Industrial Applicability

[0388] By the use of the oxide catalyst of the present invention in theoxidation or ammoxidation of propane or isobutane in the gaseous phase,(meth)acrylonitrile or (meth)acrylic acid can be produced with highselectivity and such high selectivity can be maintained for a long time,so that (meth)acrylonitrile or (meth)acrylic acid can be efficientlyproduced for a long time.

What is claimed is:
 1. An oxide catalyst for use in catalytic oxidationor ammoxidation of propane or isobutane in the gaseous phase, whichcomprises a composition represented by the following formula (I):Mo₁V_(a)Sb_(b)Nb_(c)Z_(d)O_(n)  (I) wherein: Z is at least one elementselected from the group consisting of tungsten, chromium, titanium,aluminum, tantalum, zirconium, hafnium, manganese, iron, ruthenium,cobalt, rhodium, nickel, palladium, platinum, zinc, boron, indium,germanium, tin, lead, bismuth, yttrium, gallium, rare earth elements andalkaline earth metals; and a, b, c, d, and n are, respectively, theatomic ratios of vanadium (V), antimony (Sb), niobium (Nb), Z and oxygen(O), relative to molybdenum (Mo), wherein: 0.1≦a<0.4, 0.1<b≦0.4,0.01≦c≦0.3, 0≦d≦1, with the proviso that a<b, and n is a numberdetermined by and consistent with the valence requirements of the otherelements present.
 2. The oxide catalyst according to claim 1, wherein ain formula (I) satisfies the following relationship: 0.1≦a≦0.3.
 3. Theoxide catalyst according to claim 1, wherein b in formula (I) satisfiesthe following relationship: 0.1<b≦0.35.
 4. The oxide catalyst accordingto claim 1, wherein c in formula (I) satisfies the followingrelationship: 0.05≦c≦0.2.
 5. The oxide catalyst according to claim 1,wherein a in formula (I) satisfies the following relationship:0.15≦a≦0.28.
 6. The oxide catalyst according to claim 1, wherein b informula (I) satisfies the following relationship: 0.2≦b≦0.33.
 7. Theoxide catalyst according to claim 1, wherein c in formula (I) satisfiesthe following relationship: 0.05≦c≦0.15.
 8. The oxide catalyst accordingto claim 1, wherein a, b and c in formula (I) satisfy the followingrelationships: 0.15≦a≦0.28; 0.2≦b≦0.33; 0.05≦c≦0.15; 0.5≦a+b+c≦0.69;${\frac{a}{a + b + c} \geq 0.23};\quad {and}$${0.59 - \frac{0.528a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.7 - {\frac{0.524a}{a + b + c}.}}$


9. The oxide catalyst according to claim 1, wherein a, b and c informula (I) satisfy the following relationships: 0.16≦a≦0.28;0.24≦b≦0.33; 0.07≦c≦0.15; 0.53≦a+b+c≦0.67;${\frac{a}{a + b + c} \geq 0.26};\quad {and}$${0.63 - \frac{0.549a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.68 - {\frac{0.529a}{a + b + c}.}}$


10. The oxide catalyst according to claim 1, wherein a, b and c informula (I) satisfy the following relationships: 0.16≦a≦0.26;0.24≦b≦0.30; 0.08≦c≦0.12; 0.57≦a+b+c≦0.60;${\frac{a}{a + b + c} \geq 0.28};\quad {and}$${0.67 - \frac{0.5975a}{a + b + c}} \leq \frac{b}{a + b + c} \leq {0.67 - {\frac{0.5352a}{a + b + c}.}}$


11. The oxide catalyst according to claim 1, which exhibits, in an X-raydiffraction pattern thereof obtained using CuK_(α) as a source of X-ray,peaks at diffraction angles (2θ) of: 22.1±0.3°, 28.1±0.3°, 36.1±0.3° and45.2±0.3°; 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 35.2±0.3° and45.2±0.3°; or 7.8±0.3°, 8.9±0.3°, 22.1±0.3°, 27.1±0.3°, 28.1±0.3°,35.2±0.3°, 36.1±0.3°and 45.2±0.3°.
 12. The oxide catalyst according toclaim 1, which further comprises a silica carrier having supportedthereon said oxide catalyst, wherein said silica carrier is present inan amount of from 20 to 60% by weight in terms of SiO₂, based on thetotal weight of said oxide catalyst and said silica carrier in terms ofSiO₂.
 13. The oxide catalyst according to claim 1, wherein Z in formula(I) is at least one element selected from the group consisting oftungsten, chromium, titanium, aluminum, tantalum, zirconium, iron,boron, indium, germanium and tin.
 14. The oxide catalyst according toclaim 1, which is produced by a method comprising providing an aqueousraw material mixture containing compounds of molybdenum, vanadium,antimony, niobium and optionally Z, and drying said aqueous raw materialmixture, followed by calcination.
 15. The oxide catalyst according toclaim 14, wherein the calcination is performed at 500 to 700° C. in anatmosphere of inert gas which is substantially free of molecular oxygen.16. The oxide catalyst according to claim 14, wherein said aqueous rawmaterial mixture further contains oxalic acid, wherein the molar ratioof said oxalic acid to said niobium compound in terms of niobium is inthe range of from 1 to
 10. 17. A process for producing acrylonitrile ormethacrylonitrile, which comprises reacting propane or isobutane withammonia and molecular oxygen in the gaseous phase in the presence of theoxide catalyst of claim
 1. 18. A process for producing acrylic acid ormethacrylic acid, which comprises reacting propane or isobutane withmolecular oxygen in the gaseous phase in the presence of the oxidecatalyst of claim 1.